Description

As implied from her family name, Louise is the sister of Phil and Mary-Jo Cassidy, the wife of Marty Jay Williams, the leader of a local gang (as mentioned by Phil, by way of Vic's pager), and the mother of an infant Mary-Beth Williams. Early in the game, Louise resides in the a trailer park with Marty, but grows increasingly unhappy of her rocky relationship with Marty, eventually leaving his home, taking Mary-Beth along with her, and staying in Mary-Jo's apartment in Little Havana. Marty, angered by his wife's act of hostility, attempts to kidnap her but is ultimately been killed by Victor. After Marty's death, Louise acts as a business associate and Vic's love interest during the game, although their relationship turns sour later on as Vic is often too busy to visit her.

Later on, Victor has become exceedingly busy with running his empire and working with his brother Lance, who has arrived at Vice City to try and help him. This neglect causes Louise to feel lonely and angered at him, which she deals with by spending time with Lance behind his back and adapting an addiction to cocaine. When Victor finds out about this, he becomes enraged and accuses her of having an affair with Lance and "becoming a mess", which Louise retaliates by saying he didn't care for her and bitterly tells him she doesn't want to see him anymore.

Louise fixes her relationship with Victor, however, when she is kidnapped by Jerry Martinez and beaten savagely by his men. When Victor rescues her and brings her to the hospital, they both apologize and make amends. When Louise recovers, she goes with him to rescue Lance, who has in turn been attacked by Martinez's men, and retrieved the money they had taken from him.

Louise is later killed by Armando Mendez after Armando's men kidnap her and took her to the Mendez Brothers' mansion. Armando shoots her several times and before she died, she tells Vic that she wished she and Vic had a relationship, to which Vic replied they did have something, and also told Vic that she wanted Mary-Jo to take care of her baby daughter. It is unknown what happens to her baby daughter, but she was most likely been sent to Louise's sister, Mary-Jo.